1. Field of the Invention
This invention generally relates to an illumination apparatus. More specifically, the present invention relates to a bicycle illumination apparatus capable of being connected to a power generator that generates electricity in accordance with the movement of the bicycle.
2. Background Information
Bicycling is becoming an increasingly more popular form of recreation as well as a means of transportation. Moreover, bicycling has become a very popular competitive sport for both amateurs and professionals. Whether the bicycle is used for recreation, transportation or competition, the bicycle industry is constantly improving the various components of the bicycle.
Recently, bicycles have been provided with headlights, tail lights and other bicycle illumination devices that use light-emitting diodes in order to reduce problems with bulb burnout and the like. For example, such a bicycle illumination device is disclosed in Japanese Laid-Open Patent Application No. 2005-329737. In conventional illumination devices, the light-emitting diodes are often illuminated by electricity generated with a hub dynamo placed in a wheel. Two light-emitting diodes are provided and are connected in parallel to each other in opposite directions. The AC power outputted from the hub dynamo can thereby be used without being rectified.
In the case of a resistance load, such as that of a light bulb, the electric current flowing through the light bulb is generally proportional to a voltage, in accordance with Ohm's law. However, with the load of a light-emitting diode, an electric current rapidly begins to flow at about 2 to 4 volts. In the case of only one light-emitting diode, a certain output is obtained at a low rotational speed, but when the rotational speed increases, problems are encountered in that the rate of increase in output lowers and reaches a substantial plateau. Therefore, problems are encountered in that output is insufficient when the bicycle is ridden at high speeds.
One proposal for resolving these problems is to connect multiple light-emitting diodes in series. In cases in which light-emitting diodes are connected in series, output increases with a greater number of connected light-emitting diodes because the voltage at which matching is established with the light-emitting diodes (hereinafter referred to as matching voltage) increases as the speed of the bicycle increases; i.e., as the rotational speed of the power generator increases. However, the matching voltage decreases as the rotational speed decreases. Therefore, when a generator in which multiple light-emitting diodes are connected in series is operated, sufficient voltage might not be obtainable at low traveling speeds at which the low voltage is generated.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved illumination apparatus. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.